Process for treating mineral oils



Dec. 31,1935. B. R, CARNEY Er AL 2,026,213

PROCESS FOR TREATING MINERAL OILS Filed April 5, 1955 Patented Dec. 31V,1935 UNITED `s'rrrls PATENT OFFICE signors to Shell Development Company,San Francisco, Calif., a corporation of Delaware- Application April 3,1933, Serial No. 664,118

9 Claims.

This invention relates to the methods of relining mineral oils and ismore particularly concerned with refining residual oils obtained in thecourse of producing light refined distillates such as obtained, forexample, by cracking of petroleum or its products. It is a widelypracticed method of rening the relatively light petroleum oildistillates by subjecting them to the action of a` mineral acid, such assulfuric, hydrochloric,

10 phosphoric, etc., followed by neutralization with an alkali (dry orin solution), or other basic substance, and then redistilling suchtreated distillates in order to separate the refined fractions.' ofdesired volatility from the heavier components, which either werepresent in the original distillate, or were formed as a result of thechemical treatment. These heavier components of the acid treated andneutralized distillates, when separated by distillation from the lightercomponents, form the residual oils, which unless rened, present certaindiilculties when put to further uses. As the examples of such uses,cracking of these residual oils and burning them as fuels can bementioned. The character of the difficulties encountered in connectionwith the utilization of the residual oils of this type depends, ofcourse, upon the particular use that is made of them. It is not aninfrequent occurrance, for example, that clogging of the burners andscreens is experienced when such residual oils are used as fuel; on theother hand, undesirable deposits of coke-like material with high mineralmatter content are often rapidly built up in the heating coils of thecracking furnaces, 'in which these oils are subjected to destructivedistillation or cracking.

It is the object of this invention to provide a process for treating theresidual or other oils containing reaction products o-f mineral acid and40 neutralization treatments in such amanner that their tendency to formcoke-like materials Vunder cracking conditions, or sludge-like depositsat the normal or elevated temperatures, is'materially reduced o-rpractically eliminated.

Another object of this invention is to provide the particular conditionsfor carrying out the process above referred to to the best advantage.

WhileY the method of this invention has been found Very effective forimproving qualities of Various oils containing reaction pro-ducts ofacid treated mineral oil distillate with an alkaline substance, such asacid treated and neutralized gasolines, kerosenes, stove oils, etc., orthe residues from their distillation, it was found particularlyusefulforrefining the distillation bottoms of the cracked sulfuric acid treatedneutralized distillates. The composition of these residual oils is quitecomplex, involving organic, mineral, and organo-mineral substances, someof which are present in a colloidal or otherwise nely dis- 5 persed formnot readily separable from the oil by prolonged settling. Thesesubstances (which among other compounds include alkali soaps) formsludges which clog burners, or screens in` the fuel lines, when the oilis used for fuel, or l0 cause so called coking of apparatus, if the oilis again subjected to heating. Generally, the detrimental effect of theacid` and alkali treatments followed by redistillation upon thedistillation residues increases with the intensity of acid l5 treatment,and also with the degree of the unsaturation of the raw distillates;thus it has been found that the residual oils, containing reactionproducts after treatment with sulfuric acid of over 90% strength, and/orproduced from cracked 20 distillates which contained 40% by volume o-rmore unsaturates (98% H2804 absorption method), usually containrelatively large amounts of screen clogging and/or other objectionablematerial, but respond very readily to the treatment 25 of this inventionwith great reduction or elimination of screen clogging tendency or cokeformation on heating. While the mechanism of the refining action is notentirely clear, it is believed that removal of the objectionable oilcomponents, 30 aswell as their chemical transformations, are involved inthis treating process.

According to the present invention, the oils containing undesirablesubstances, which apparently are'the reaction products referred toabove, are 35 intimately contacted with a brine containing a substantialquantity of NaCl and/ or other suitable mineral salts such as CaC12whereafter the oilbrine mixture is allowed to settle and the refined oilis separated from the aqueous layer.

The details of the treatment will be further understood from thefollowing description which is set forth by way of example only, withoutbeing intended to limit the scope of the invention. The iiow of thevarious liquids used in the process is 45 diagrammatically shown in Fig.1 of the drawing.

A cracked distillate with a gasoline content of about boiling up toabout 560 F. and containing about 50% unsaturates, is drawn from a tankI and subjected to a treatment in an agi- 50 tator 2 with about 3 lbs.of 93% H2SO4 from tank 3 per barrel of the distillate. The sludge isWithdrawn by means of a line 4 and the treated oil is thoroughly waterwashed in a tank 5 and neutralized in a treater 6 with a causticsolution from 55 a tank 7. The resulting treated distillate isredistilled, for example, in a fractionating column 8 to eliminate lowboiling fractions, which are removed by means of pipe 9, and the residue(an oil of about 26 A. P. I. gravity) is drawn through line I0, and issubjected to a treatment to remove the screen clogging material andother objectionable components. Prior to this treatment it may beascertained that the residual oil is substantially neutral, i. e., hasan acid indication with phenolphthalein and an alkaline reaction withmethyl orange indicators. This neutral residual oil is then treated withabout 20% of its volume of a 50% saturated aqueous NaCl solution in anagitator or agitators, such as I I, I2 and I3, the temperature beingmaintained at about 150 F. The mixture is then conducted to a settlingtank I4 and allowed to settle therein while at about the sametemperature. An interphase layer of sludge like material is formed uponsettling. Next, the brine, the sludge and the refined oil layers areseparated, the latter being conducted to storage or to some otherdestination such as a cracking still or a furnace.

An improved process may consist in passing countercurrent streams of theoil being treated and of the treating brine through a series of mixingand separating devices, so that, for example, the raw oil is rstcontacted with a substantially spent salt solution in agitator II, ispartly refined thereby, separated, and then contacted again in a seriesof similar steps with progressively more effective or fresher saltsolutions until, finally, the practically completely rened oil iscontacted with fresh brine from tank I5 in agitator I3, separatedtherefrom, and conducted to the settling tank I4.

The efficiency of the process may be considerably increased by usingcentrifugal mixers and separators, wherein the unrefined oil and thebrine are quickly and effectively contacted, the rened oil being thenseparated from the spent brine. Such an operation considerably increasesthe throughput of a plant and permits a continuous operation. It hasbeen demonstrated that the quality of the oil is greatly improved bythis brine treatment.

The particular method for evaluating the tendency of a fuel oil to clogburners and screens involved the use of an apparatus which consisted ofan oil container (about 1 gallon capacity) connected through a bottomoutlet to a long vertical tube provided at its lower end with a smallopening over which was placed a screen of 60 mesh. The oil was passed bygravity from the container through this small opening in 500 cc.portions, and the time required for passing each portion was noted.After withdrawal of each portion an equal quantity of unscreened oil wasadded to the container and the rate of ow for the next 500 cc. portionwas then determined. A substantially constant oil temperature within therange 'l0-80 F. was maintained during the tests. From thesedeterminations a chart shown on Fig. 2 of the drawing was constructedwherein the gradually decreasing rates of flow (due to clogging of thescreen), expressed in terms (percent) of the initial rate of flow(100%), were plotted against the amount of the oil discharged throughthe graphically represented on the accompanying diagram. It is observedthat the residual oil, as taken from the still, clogged the screen after3200 cc. of it was discharged, while the oil'"treated according to thisinvention flowed freely even after a Very large quantity of it waspassed through.

Referring now to certain particulars concerning practicing theinvention, it should be noted that while it is possible to employ inthis process brines containing less than 50% of salt saturation, it ispreferable to use more concentrated solutions, containing over 50% saltsaturation; such conu) centrated solutions have much less tendency toform emulsions with the oils than more dilute ones.

It is quite important for an efficient operation of the treatment tosubject to agitation the oil- 15 brine mixture which has neutralreaction, 1. e., acid to phenolphthalein and'alkaline to methyl orange;it is preferable that this be brought about by making both the oil andthe brine to react neutral before mixing them together. The inten- 20sity of agitation and the time of contact of the oil with the brineshould be regulated so as to effect bringing together of substantiallyevery particle of the oil being treated with a body of brine,whereby therefining action of the brine 25 is assured.

. The temperature of treatment has a considerable bearing upon theeifectiveness of the rening. In general, it is preferable to contact andseparate the oil and the brine at slightly elevated l temperatures; ithas been discovered, that the temperatures within the range 1Z0-200 F.,and especially 14C-170 F., are particularly favorable for quicklybreaking and settling the mixtures produced by stirring the reactingmaterials. 35

Having fully described the process of our in- Vention, we claim as newand useful:

'1. A process of refining a mineral oil which has been treated with amineral acid and neutralized with an alkali, comprising, contacting theoil with the concentrated aqueous solution of a salt selected from thefollowing group: sodium chloride and calcium chloride, and thenseparating the oil from said solution.

2. The process as in claim l, wherein the acid 45,

treated oil has been produced by treating an oil with sulfuric acid.

3. The process as in claim 1, wherein the acid treated oil has beenproduced by treating an oil with sulfuric acid of not less than concen-50 tration.

4. The process as in claim 1, wherein the oil to be refined containsreaction products resulting from neutralization of an oil treated withsulfuric acid by means of sodium hydroxide.

5. A process of refining a mineral oil which comprises, contacting theoil with a mineral acid, thereby separating acid soluble oil componentsinto a sludge and producing an acid treated oil, separating the latterfrom the sludge, neutraliz- 60 ing the acid treated oil, and thentreating the neutral oil with the concentrated aqueous solution of asalt selected from the following group:

sodium chloride and calcium chloride.

6. The process as in claim 5, wherein treat- 65 trating said products inthe oil by distilling oif a. 75.

portion of the neutralized oil, and then freeing the remaining portionof the oil from said objectionable reaction products by treating saidportions with the aqueous solution of a salt selected from the followinggroup: sodium chloride and calcium chloride. Y

8. Continuous process for rening a cracked oil containing reactionproducts of acid and alkali treatments, which comprises, maintainingcontinuous countercurrent streams of the oil and the concentratedaqueous solution of a salt selected fro-m the following group: sodiumchloride and calcium chloride, and repeatedly contacting and separatingsaid oil and solution in a series of steps in such a manner that unrenedoil is contacted with a substantially exhausted salt solution, theresulting partly purifled oil is contacted with a partly exhausted saltsolution, and the resulting substantially purified oil is contacted witha fresh salt solution.

9. A process of rening a mineral oil, which has been treated with amineral acid and neutralized with an alkali, comprising contacting theoil with the aqueous solution of a salt selected from the followinggroup: sodium chloride and calcium chloride, said solution being of atleast 50%'saturation, and then separating the refined oil from theaqueous solution.

BERNARD RICHARD CARNEY. RALPH HOAGLAND CROSBY.

